The Chemical Biology-Medicinal Chemistry Continuum: EFMC's Vision.

The European Federation for Medicinal chemistry and Chemical biology (EFMC) is a federation of learned societies. It groups organizations of European scientists working in a dynamic field spanning chemical biology and medicinal chemistry. New ideas, tools, and technologies emerging from a wide array of scientific disciplines continuously energize this rapidly evolving area. Medicinal chemistry is the design, synthesis, and optimization of biologically active molecules aimed at discovering new drug candidates - a mission that in many ways overlaps with the scope of chemical biology. Chemical biology is by now a mature field of science for which a more precise definition of what it encompasses, in the frame of EFMC, is timely. This article discusses chemical biology as currently understood by EFMC, including all activities dealing with the design and synthesis of biologically active chemical tools and their use to probe, characterize, or influence biological systems.

Prognostic significance of serum inflammatory markers in esophageal cancer.

BACKGROUND: The aim of this study was to assess the relative prognostic value of biomarkers to measure the systemic inflammatory response (SIR) and potentially improve prognostic modeling in patients undergoing potentially curative surgery for esophageal adenocarcinoma (EC). METHODS: Consecutive 330 patients undergoing surgery for EC between 2004 and 2018 within a regional UK cancer network were identified. Serum measurements of haemoglobin, C-reactive protein, albumin, modified Glasgow Prognostic Score (mGPS), and differential neutrophil to lymphocyte ratio (NLR) were obtained before surgery, and correlated with histopathological factors and outcomes. Primary outcome measures were disease-free (DFS) and overall survival (OS). RESULTS: Of 330 OC patients, 294 underwent potentially curative esophagectomy. Univariable DFS analysis revealed pT, pN, pTNM stage (all p < 0.001), poor differentiation (p = 0.001), vascular invasion (p < 0.001), R1 status (p < 0.001), perioperative chemotherapy (p = 0.009), CRP (p = 0.010), mGPS (p = 0.011), and NLR (p < 0.001), were all associated with poor survival. Multivariable Cox regression analysis of DFS revealed only NLR [Hazard Ratio (HR) 3.63, 95% Confidence Interval (CI) 2.11-6.24, p < 0.001] retained significance. Multivariable Cox regression analysis of OS revealed similar findings: NLR [HR 2.66, (95% CI 1.58-4.50), p < 0.001]. CONCLUSION: NLR is an important SIR prognostic biomarker associated with DFS and OS in EC.

Epstein-Barr Virus-Positive Mucocutaneous Ulcers Complicate Colitis Caused by Immune Checkpoint Regulator Therapy and Associate With Colon Perforation.

BACKGROUND & AIMS: Cancer therapy with immune checkpoint inhibitors can cause colitis and colon perforation. We investigated whether infection with Epstein Barr virus (EBV) associates with development and severity of colitis in patients receiving immune checkpoint inhibitor therapies. METHODS: We performed a retrospective analysis of fixed colon tissues from 16 patients (12 men, 4 women, median age, 69.5 y) with colitis after immune checkpoint inhibitor therapy (9 patients treated with anti-CTLA4, 3 patients treated with anti-PD1, and 4 patients received a combination). Ten tissue samples were biopsies and 6 were collected during resection (4 surgeries for colon perforation). Patients were treated between 2010 and 2018 in the United Kingdom. The tissues were analyzed by pathology, in situ hybridization (to detect EBV-encoded small RNAs [EBERs]), and immunohistochemistry. Clinical data were also collected. RESULTS: Colon tissues from 4 of the 13 patients who received anti-CTLA4 (alone or in combination, 4 with colon perforation) had EBV-positive lymphoproliferations that manifested as florid ulcers associated with polymorphous infiltrates containing EBV-positive blasts (CD30+ or CD30-negative, CD20+, CD3-negative, and EBER+), plasma cells (CD138+, CD20-negative, and EBER+ or EBER-negative), and small B cells (CD20+, CD3-negative, and EBER+ or EBER-negative), consistent with EBV-positive mucocutaneous ulcers (EBVMCUs). In analyses of biopsies collected from 2 patients with EBVMCUs over multiple time points, we found that earlier biopsies had no or only a few EBV-positive cells, whereas 1 later biopsy had EBVMCU and co-infection with cytomegalovirus. EBVMCUs were associated with steroid-refractory colitis (100% of EBV-positive patients vs 12.5% of EBV-negative patients; P = .008) and colon perforation (100% of EBV-positive patients vs no EBV-negative patients; P = .001). CONCLUSIONS: We found that colon tissues from 4/13 patients with colitis after anti-CTLA4 therapy (4/6 patients who underwent resection and 4/4 patients with colon perforation) contained EBVMCUs. EBVMCUs seem to arise secondarily in areas of inflamed colon due to immunosuppressive treatment for colitis. EBVMCUs are associated with steroid-refractory colitis and colon perforation.

The nature of the human T cell response to the cancer antigen 5T4 is determined by the balance of regulatory and inflammatory T cells of the same antigen-specificity: implications for vaccine design.

The oncofoetal antigen 5T4 is a promising T cell target in the context of colorectal cancer, as demonstrated by a recent clinical study where 5T4-specific T cell responses, induced by vaccination or cyclophosphamide, were associated with a significantly prolonged survival of patients with metastatic disease. Whilst Th1-type (IFN-γ+) responses specific to 5T4, and other oncofoetal antigens, are often readily detectable in early stage CRC patients and healthy donors, their activity is suppressed as the cancer progresses by CD4+CD25hiFoxp3+ regulatory T cells (Treg) which contribute to the immunosuppressive environment conducive to tumour growth. This study mapped the fine specificity of Th1 and Treg cell responses to the 5T4 protein. Surprisingly, both immunogenic peptides and those recognised by Tregs clustered in the same HLA-DR transcending epitope-rich hotspots within the 5T4 protein. Similarly, regions of low Th1-cell immunogenicity also did not contain peptides capable of stimulating Tregs, further supporting the notion that Treg and Th1 cells recognise the same peptides. Understanding the rules which govern the balance of Th1 and Treg cells responding to a given peptide specificity is, therefore, of fundamental importance to designing strategies for manipulating the balance in favour of Th1 cells, and thus the most effective anti-cancer T cell responses.

The paradox of NKp46+ natural killer cells: drivers of severe hepatitis C virus-induced pathology but in-vivo resistance to interferon α treatment.

OBJECTIVE: There is evidence that natural killer (NK) cells help control persistent viral infections including hepatitis C virus (HCV). The phenotype and function of blood and intrahepatic NK cells, in steady state and after interferon (IFN) α treatment has not been fully elucidated. DESIGN: We performed a comparison of NK cells derived from blood and intrahepatic compartments in multiple paired samples from patients with a variety of chronic liver diseases. Furthermore, we obtained serial paired samples from an average of five time points in HCV patients treated with IFNα. RESULTS: Liver NK cells demonstrate a distinct activated phenotype compared to blood manifested as downregulation of the NK cell activation receptors CD16, NKG2D, and NKp30; with increased spontaneous degranulation and IFN production. In contrast, NKp46 expression was not downregulated. Indeed, NKp46-rich NK populations were the most activated, correlating closely with the severity of liver inflammation. Following initiation of IFNα treatment there was a significant increase in the proportion of intrahepatic NK cells at days 1 and 3. NKp46-rich NK populations demonstrated no reserve activation capacity with IFNα treatment and were associated with poor viral control on treatment and treatment failure. CONCLUSIONS: NKp46 marks out pathologically activated NK cells, which may result from a loss of homeostatic control of activating receptor expression in HCV. Paradoxically these pathological NK cells do not appear to be involved in viral control in IFNα-treated individuals and, indeed, predict slower rates of viral clearance.

EUS-FNA diagnosis of a pancreatic lymphoepithelial cyst: three-year imaging follow-up.

CONTEXT: Lymphoepithelial cyst of the pancreas is a rare benign lesion that should be managed conservatively. Similarity has been described between lymphoepithelial cyst and a branchial cyst of the neck. CASE REPORT: We report a 58-year-old man presenting with left sided abdominal pain initially thought to be renal colic. CT of the abdomen revealed a 3.5 cm lesion in the pancreatic tail. A laparoscopic distal pancreatectomy was initially planned for definitive treatment; however, endoscopic ultrasound guided fine needle aspiration (EUS-FNA) was performed prior to surgery as he had multiple co-morbidities. This confirmed the diagnosis of lymphoepithelial cyst, a benign lesion. Unnecessary high-risk surgery was therefore avoided. Three year follow-up has shown no adverse effects and the lymphoepithelial cyst is unchanged in size and appearance. CONCLUSION: EUS-FNA is a reliable method to confidently diagnose lymphoepithelial cyst and therefore should be used to exclude malignancy, thus avoiding unnecessary surgery with potential complications.

Prediction of lymph node metastases using pre-treatment PET radiomics of the primary tumour in esophageal adenocarcinoma: an external validation study.

OBJECTIVES: To improve clinical lymph node staging (cN-stage) in oesophageal adenocarcinoma by developing and externally validating three prediction models; one with clinical variables only, one with positron emission tomography (PET) radiomics only, and a combined clinical and radiomics model. METHODS: Consecutive patients with fluorodeoxyglucose (FDG) avid tumours treated with neoadjuvant therapy between 2010 and 2016 in two international centres (n = 130 and n = 60, respectively) were included. Four clinical variables (age, gender, clinical T-stage and tumour regression grade) and PET radiomics from the primary tumour were used for model development. Diagnostic accuracy, area under curve (AUC), discrimination and calibration were calculated for each model. The prognostic significance was also assessed. RESULTS: The incidence of lymph node metastases was 58% in both cohorts. The areas under the curve of the clinical, radiomics and combined models were 0.79, 0.69 and 0.82 in the developmental cohort, and 0.65, 0.63 and 0.69 in the external validation cohort, with good calibration demonstrated. The area under the curve of current cN-stage in development and validation cohorts was 0.60 and 0.66, respectively. For overall survival, the combined clinical and radiomics model achieved the best discrimination performance in the external validation cohort (X2 = 6.08, df = 1, p = 0.01). CONCLUSION: Accurate diagnosis of lymph node metastases is crucial for prognosis and guiding treatment decisions. Despite finding improved predictive performance in the development cohort, the models using PET radiomics derived from the primary tumour were not fully replicated in an external validation cohort. ADVANCES IN KNOWLEDGE: This international study attempted to externally validate a new prediction model for lymph node metastases using PET radiomics. A model combining clinical variables and PET radiomics improved discrimination of lymph node metastases, but these results were not externally replicated.

Cancer Antigen Discovery Is Enabled by RNA Sequencing of Highly Purified Malignant and Nonmalignant Cells.

PURPOSE: Broadly expressed, highly differentiated tumor-associated antigens (TAA) can elicit antitumor immunity. However, vaccines targeting TAAs have demonstrated disappointing clinical results, reflecting poor antigen selection and/or immunosuppressive mechanisms. EXPERIMENTAL DESIGN: Here, a panel of widely expressed, novel colorectal TAAs were identified by performing RNA sequencing of highly purified colorectal tumor cells in comparison with patient-matched colonic epithelial cells; tumor cell purification was essential to reveal these genes. Candidate TAA protein expression was confirmed by IHC, and preexisting T-cell immunogenicity toward these antigens tested. RESULTS: The most promising candidate for further development is DNAJB7 [DnaJ heat shock protein family (Hsp40) member B7], identified here as a novel cancer-testis antigen. It is expressed in many tumors and is strongly immunogenic in patients with cancers originating from a variety of sites. DNAJB7-specific T cells were capable of killing colorectal tumor lines in vitro, and the IFNγ+ response was markedly magnified by control of immunosuppression with cyclophosphamide in patients with cancer. CONCLUSIONS: This study highlights how prior methods that sequence whole tumor fractions (i.e., inclusive of alive/dead stromal cells) for antigen identification may have limitations. Through tumor cell purification and sequencing, novel candidate TAAs have been identified for future immunotherapeutic targeting.

Cyclo-oxygenase-2 expression is associated with mean standardised uptake value on 18F-Fluorodeoxyglucose positron emission tomography in oesophageal adenocarcinoma.

OBJECTIVES: This pilot study investigated the association of four PET image features and cyclo-oxygenase-2 (COX-2) expression in patients with oesophageal adenocarcinoma. The prognostic significance of these biomarkers was also assessed. METHODS: 50 consecutive patients [median age = 68 (range 47 - 84), males = 45) with oesophageal adenocarcinoma had PET/CT staging between January 2011 and July 2015. The maximum and mean standardised uptake values (SUVmax and SUVmean), metabolic tumour volume (MTV) and tumour lesion glycolysis (TLG) were calculated from the primary tumour. Their association with COX-2 status was assessed using Mann-Whitney U tests. Kaplan-Meier and Cox regression analysis tested their prognostic significance. A p-value < 0.05 was considered statistically significant. RESULTS: 32 tumours (64.0%) were COX-2 positive. There was a significant association between SUVmean and COX-2 status (p = 0.019). TLG (hazard ratio (HR) 1.001, 95 % confidence intervals (CI) 1.000 - 1.002, p = 0.018) was significantly associated with overall survival on multivariable analysis. CONCLUSIONS: This study investigated the association between PET image features and COX-2 expression in oesophageal adenocarcinoma. The preliminary results signal that a combination of TLG (calculated as product of MTV and SUVmean) and COX-2 status may be a strong and clinically important prognostic biomarker. Our research group are planning a prospective, multi-centre study to validate these findings. ADVANCES IN KNOWLEDGE: Mean standardised uptake value (SUVmean) on PET imaging is associated with COX-2 expression in oesophageal adenocarcinoma.

Retrospective study on mixed neuroendocrine non-neuroendocrine neoplasms from five European centres.

BACKGROUND: Mixed neuroendocrine non-neuroendocrine neoplasm (MiNEN) is a rare diagnosis, mainly encountered in the gastro-entero-pancreatic tract. There is limited knowledge of its epidemiology, prognosis and biology, and the best management for affected patients is still to be defined. AIM: To investigate clinical-pathological characteristics, treatment modalities and survival outcomes of a retrospective cohort of patients with a diagnosis of MiNEN. METHODS: Consecutive patients with a histologically proven diagnosis of MiNEN were identified at 5 European centres. Patient data were retrospectively collected from medical records. Pathological samples were reviewed to ascertain compliance with the 2017 World Health Organisation definition of MiNEN. Tumour responses to systemic treatment were assessed according to the Response Evaluation Criteria in Solid Tumours 1.1. Kaplan-Meier analysis was applied to estimate survival outcomes. Associations between clinical-pathological characteristics and survival outcomes were explored using Log-rank test for equality of survivors functions (univariate) and Cox-regression analysis (multivariable). RESULTS: Sixty-nine consecutive patients identified; Median age at diagnosis: 64 years. Males: 63.8%. Localised disease (curable): 53.6%. Commonest sites of origin: colon-rectum (43.5%) and oesophagus/oesophagogastric junction (15.9%). The neuroendocrine component was; predominant in 58.6%, poorly differentiated in 86.3%, and large cell in 81.25%, of cases analysed. Most distant metastases analysed (73.4%) were occupied only by a poorly differentiated neuroendocrine component. Ninety-four percent of patients with localised disease underwent curative surgery; 53% also received perioperative treatment, most often in line with protocols for adenocarcinomas from the same sites of origin. Chemotherapy was offered to most patients (68.1%) with advanced disease, and followed protocols for pure neuroendocrine carcinomas or adenocarcinomas in equal proportion. In localised cases, median recurrence free survival (RFS); 14.0 mo (95%CI: 9.2-24.4), and median overall survival (OS): 28.6 mo (95%CI: 18.3-41.1). On univariate analysis, receipt of perioperative treatment (vs surgery alone) did not improve RFS (P = 0.375), or OS (P = 0.240). In advanced cases, median progression free survival (PFS); 5.6 mo (95%CI: 4.4-7.4), and median OS; 9.0 mo (95%CI: 5.2-13.4). On univariate analysis, receipt of palliative active treatment (vs best supportive care) prolonged PFS and OS (both, P < 0.001). CONCLUSION: MiNEN is most commonly driven by a poorly differentiated neuroendocrine component, and has poor prognosis. Advances in its biological understanding are needed to identify effective treatments and improve patient outcomes.

Prognostic Significance of Post-Operative Morbidity Severity Score After Potentially Curative D2 Gastrectomy for Carcinoma.

BACKGROUND: Survival and relapse after gastric cancer surgery are largely attributed to tumor biology and surgical radicality; yet, other prognostic factors have been reported, including respiratory sepsis and anastomotic leakage, but not global morbidity severity score (MSS). The hypothesis tested was that MSS would be associated with both disease-free (DFS) and overall survival (OS). METHODS: Consecutive 373 patients undergoing potentially curative surgery for gastric adenocarcinoma between 2004 and 2016 in a UK cancer network were studied. Complications were defined prospectively as any deviation from a pre-determined post-operative course within 30 days of surgery and classified according to the Clavien-Dindo severity classification (CDSC). Primary outcome measures were DFS and OS. RESULTS: Post-operative complications were identified in 127 (34.0%) patients, which was associated with 9 (2.4%) post-operative deaths. Five-year DFS and OS were 35.9 and 38.5% for patients with a post-operative complication compared with 59.5 and 61.5% in controls (p < 0.001, p = 0.001, respectively). On multivariable DFS analysis, post-operative morbidity [hazard ratio (HR) 1.63, 95% confidence interval (CI) 1.06-2.50, p = 0.026] was independently associated with poor survival. On multivariable OS analysis, post-operative morbidity HR 2.25 (95% CI 1.04-4.85, p = 0.039) and CDSC HR 1.76 (95% CI 1.35-2.29, p < 0.001) were independently associated with poor survival. These associations were also observed in patients with TNM stage I and II disease with morbidity HR 7.06 (95% CI 1.89-26.38, p = 0.004) and CDSC HR 2.93 (95% CI 1.89-4.55, p < 0.001) offering independent prognostic value. CONCLUSION: Post-operative CDSC was an important independent prognostic factor after potentially curative gastrectomy for carcinoma associated with both DFS and OS. Prehabilitation strategies to minimize complications are warranted.

Prognostic Significance of Serum Inflammatory Markers in Gastric Cancer.

BACKGROUND: The aim of this study was to assess the relative prognostic value of biomarkers to measure the systemic inflammatory response (SIR) and improve prognostic modeling in a cohort of patients undergoing potentially curative surgery for gastric adenocarcinoma. The hypothesis was that a single SIR biomarker would be associated with the most prognostic value. METHODS: Consecutive 331 patients undergoing surgery for gastric cancer between 2004 and 2016 within a regional UK cancer network were identified. Serum measurements of hemoglobin, C-reactive protein, albumin, modified Glasgow Prognostic Score, and differential white cell counts were obtained before surgery, and correlated with histopathological factors (pTNM stage, differentiation, and vascular invasion) and survival. Primary outcome measures were disease-free (DFS) and overall survival (OS). RESULTS: Consecutive 331 patients were identified and 291 underwent potentially curative gastrectomy for adenocarcinoma. On univariable DFS analysis, female gender (p = 0.027), proximal location (p = 0.018), pT stage (p < 0.001), pN stage (p < 0.001), pTNM stage (p < 0.001), vascular invasion (p < 0.001), poor differentiation (p = 0.001), lymph node ratio (p < 0.001), R1 status (p < 0.001), platelet count (p = 0.038), and mGPS (p = 0.001) were significantly associated with poor survival. The mGPS was associated with advanced pT stage (p = 0.001), pTNM stage (p = 0.013), and poor differentiation (p = 0.030). On multivariable DFS analysis, mGPS [hazard ratio (HR) 2.51, 95% confidence interval (CI) 1.35-4.65, p = 0.011] was the only inflammatory marker to retain independent significance. Multivariable OS analysis revealed similar findings; mGPS (HR 2.75, (95% CI 1.65-4.59), p < 0.001). CONCLUSION: mGPS is an important and only SIR-related prognostic biomarker independently associated with both DFS and OS in gastric cancer.

Sensitivity to inhibition of DNA repair by Olaparib in novel oropharyngeal cancer cell lines infected with Human Papillomavirus.

The incidence of Human Papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) is increasing rapidly in the UK. Patients with HPV-positive OPSCC generally show superior clinical responses relative to HPV-negative patients. We hypothesised that these superior responses could be associated with defective repair of DNA double strand breaks (DSB). The study aimed to determine whether defective DNA repair could be associated with sensitivity to inhibition of DNA repair using the PARP inhibitor Olaparib. Sensitivity to Olaparib, and induction and repair of DNA damage, were assessed in a panel of 8 OPSCC cell-lines, including 2 novel HPV-positive lines. Effects on cell cycle distribution and levels of PARP1 and p53 were quantified. RNA-sequencing was used to assess differences in activity of DNA repair pathways. Two HPV-positive OPSCC lines were sensitive to Olaparib at potentially therapeutic doses (0.1-0.5 µM). Two HPV-negative lines were sensitive at an intermediate dose. Four other lines, derived from HPV-positive and HPV-negative tumours, were resistant to PARP inhibition. Only one cell-line, UPCISCC90, showed results consistent with the original hypothesis i.e. that in HPV-positive cells, treatment with Olaparib would cause accumulation of DSB, resulting in cell cycle arrest. There was no evidence that HPV-positive tumours exhibit defective repair of DSB. However, the data suggest that a subset of OPSCC may be susceptible to PARP-inhibitor based therapy.

Aptamer Selection against a Trichomonas vaginalis Adhesion Protein for Diagnostic Applications.

Trichomoniasis, caused by Trichomonas vaginalis, is the leading nonviral sexually transmitted infection worldwide. We report the selection of a DNA aptamer against a T. vaginalis adhesion protein, AP65, using a microtiter plate-based in vitro combinatorial chemistry process termed systematic evolution of ligands by exponential enrichment. The enriched library pool was sequenced by next-generation sequencing, and several aptamer candidates with high affinity and specificity were identified. The aptamer with the highest affinity and specificity had a KD in the low nanomolar range, as confirmed by three different techniques: surface plasmon resonance, enzyme-linked aptamer assay, and biolayer interferometry. The selected aptamer was demonstrated to have a high specificity to the AP65 protein and to T. vaginalis cells with no cross-reactivity to other enteric and urogenital microorganisms. Current work is focused on the development of inexpensive and easy-to-use aptamer-based diagnostic assays for the reliable and rapid detection of T. vaginalis in vaginal swabs.

Intestinal spirochaetosis causing chronic diarrhoea in a patient with HIV infection.

A 36-year-old Caucasian homosexual man was found to have HIV infection on routine screening. He had an eight-year history of chronic diarrhoea, which pre-dated the HIV diagnosis and did not improve after the introduction of combination antiretroviral therapy. After referral to the Gastroenterology department, he underwent fibreoptic colonoscopy. Colonic biopsies revealed the presence of intestinal spirochaetosis. He received a two-week course of metronidazole, which led to complete resolution of his diarrhoea. Intestinal spirochaetosis should be considered in the differential diagnosis of patients with HIV infection and chronic diarrhoea without other apparent cause.

Histological analysis of cervical intraepithelial neoplasia.

A wide interobserver variation is seen even among competent histopathologists in the routine diagnosis of cervical intraepithelial neoplasia (CIN). As a result, early detection of low-grade CIN (CIN 1) lesions, in particular, remains a major challenge both in routine diagnosis and in cervical screening. In this chapter, the salient diagnostic features of human papillomavirus infection and CIN lesions are demonstrated.

Escalating regulation of 5T4-specific IFN-γ+ CD4+ T cells distinguishes colorectal cancer patients from healthy controls and provides a target for in vivo therapy.

The relationship between the adaptive CD4+ T cell response and human cancer is unclear. The oncofetal antigen 5T4 is expressed on many human carcinomas, including colorectal cancer (CRC) cells, but has limited expression on normal tissues. We previously identified anti-5T4 CD4+ T cells in a proportion of CRC patients, and we extended this study to examine whether the quality or quantity of the T cell response reflects tumor stage. An overlapping peptide library spanning 5T4 was used as a target to enumerate cognate IFN-γ+CD4+ T-cells (measured as spot forming cells [SFC]/105 cultured T cells) in peripheral blood-derived lymphocytes following a 12-day in vitro culture period comparing patients pre-operatively (n = 27) to healthy controls (n = 17). Robust 5T4-specific T cell responses were present in 100% of healthy donors. There was a steady loss of T cell responses with advancing tumors with a significant negative correlation from stage I to III (P = 0.008). The predictability of the decline meant < 200 SFC/105 was only found in subjects with stage III CRC. The mechanism of loss of T cell response is independent of HLA-DR type or patient age, but does correspond to increases in Foxp3+ regulatory T cells (Tregs). Using low-dose cyclophosphamide to reduce the proportion of Tregs in vivo resulted in increased anti-5T4 T cell responses in CRC patients. The selective loss of 5T4-specific IFN-γ+CD4+ T cell responses implies a link between tumor stage and antitumor Th1 effector function; depleting Tregs can enhance such responses.